Date: Sat, 29 Apr 2000 13:53:50 +0200 From: Dave Boers <djb@ifa.au.dk> To: Terry Lambert <tlambert@primenet.com> Cc: Matthew Dillon <dillon@apollo.backplane.com>, Jeremiah Gowdy <jgowdy@home.com>, Steve Passe <smp@csn.net>, James Housley <jim@thehousleys.net>, freebsd-smp@FreeBSD.ORG Subject: Re: hlt instructions and temperature issues Message-ID: <20000429135350.A3919@relativity.student.utwente.nl> In-Reply-To: <200004290120.SAA11745@usr08.primenet.com>; from tlambert@primenet.com on Sat, Apr 29, 2000 at 01:20:13AM %2B0000 References: <200004282240.PAA14200@apollo.backplane.com> <200004290120.SAA11745@usr08.primenet.com>
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On Sat, Apr 29, 2000 at 01:20:13AM +0000, Terry Lambert wrote:
> I think the numbers for a 2 CPU system with Loqui's patch were
> extremely exagerated by the CPU stalling-until-interrupt issue,
> and that the heat numbers will not be nearly so good, even on a
> totally "correct" solotuion because of this. I expect your
> approach would result in temeperatures nearly as high, if not
> downright indistinguishable from, the measured numbers for an
> unmodified system.
To further input some experimental facts into this discussion, I have
applied Luoqi Chen's patch and I'm testing it now. The system (Abit BP6
dual Celeron) has been up for nearly 14 hours now, mostly being idle.
The temperature has dropped dramatically: from 50 degrees Celcius to 27
degrees Celcius. Look at that: 23 degrees temperature difference! Besides,
27 degrees is almost the same temperature as my single Celeron unit (which
has only 3 fans while my dual box has 6 of them.
Also, diagnostics report that the core voltage has risen by 0.05 Volt as a
consequence of the reduced power consumption of the CPU's.
The kernel looks stable, even though from the thread I get the impression
that many problems might arise. To stress the system somewhat, I'll do a
make -j 12 buildworld now. See if it crashes.
> This is really not an issue, anyway, except for power consumption
> and heat dissipation critical environments, but that said, if it's
> for an SMP box going into a colocation server room rack somewhere
> in a 1U case, this could be significant for some percentage of
> users, so maybe it's worth still talking about. 8-).
Excuse me, but I think this *is* an issue worth talking about.
My SMP box is in a full tower server housing. Each CPU has a (normal size)
fan, two fans are cooling the harddrives (which are in the top of the
case), one fan (in the PS) cools the mainboard and processor area and
finally there is one fan (in the bottom of the case) blowing cool air into
the case and directly at the hottest PCI cards. Not even all this is enough
to cool the processors to a decent temperature if I'm running the
unmodified kernel. Though I have made a special order for some globalwin
king size cpu fans, I'd much rather have my sustem produce less heat by
running hlt instructions.
For extra clarity, let me point out that I my system is *not* overclocked
and environmental temperatures for all measurements are between 21 and 24
degrees Celcius.
Every bit of heat my system produces will have to be pumped away by the
airconditioning which is having a hard time on hot days. And also consider
the overall waste of electrical energy by all the SMP systems running
FreeBSD around the world. I think this is a big issue.
Regards,
Dave Boers.
P.S. Let me add that for me being a theoretical (computational) physicist
it's kind of funny to be on the experimental side for a change!
--
djb@ifa.au.dk d.j.boers@tn.utwente.nl
PGP key: ftp://relativity.student.utwente.nl:/pub/pgpkeys/djb.asc
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